The invention relates to a method for obtaining lipids with a high proportion of long-chain highly unsaturated fatty acids, with from 20 to 22 carbon atoms, by extraction from a raw material of animal or vegetable origin, and to the extract obtained and its use.
1. Field of the Invention
Our foodstuffs include not only saturated fatty acids but also monounsaturated and polyunsaturated fatty acids, which thus have at least one double bond in their carbon chain. These polyunsaturated fatty acids are often designated by abbreviations. The number of carbon atoms or the chain length is given first. This is followed by a hyphen or colon, which in turn is followed by a number that indicates how many double bonds there are in the carbon chain. Following that but separately, the number of omega-carbon atoms is given, counted from the methyl end of the chain, after a "w" or "n". In this system, the short formula for linoleic acid is 18-2 n6.
In fatty acid metabolism in the human being, double bonds are known to be introduced into the carbon chain of a saturated fatty acid. However, this desaturation is possible only after the carbon atom C9 in the direction toward the carboxyl end. The result is that fatty acids such as linoleic acid (18:2 n6) and .alpha.-linolenic acid (18:3 n3) must be considered essential, since they cannot be synthesized by the human organism itself but rather must be supplied from food.
From these essential C18 fatty acids, the healthy human organism is capable of synthesizing a number of polyunsaturated fatty acids having from 20 to 22 carbon atoms, by means of further desaturation and chain elongation. The elongation occurs at the carboxyl end of the molecule, and the desaturation occurs between the carboxyl group and the first double bond that follows it. The number of carbon atoms between the methyl end of the fatty acid and the last double bond (omega-C atoms) remains unchanged thereby, so that from linoleic acid (18:2 n6) in lipid metabolism, only omega-6 fatty acids (w6 family) are derived, and from .alpha.-linolenic acid only-omega-3 fatty acids (w3 family) are derived. The course of biosynthesis of the w6 family thus begins with linoleic acid (C 18-2 n6) and proceeds through gamma-linolenic acid (C 18-3 n6), di-homo-gamma-linolenic acid (C20-3 n6), and arachidonic acid (C20-4 n6) to docosapentanoic acid (C22-5 n6). With respect to the w3 family, the course of biosynthesis begins with .alpha.-linolenic acid (C18-3 n3), through octadecatetraenoic acid (C18-4 n3), eicosatetranoic acid (C20-4 n3), eicosapentanoic acid (C20-5 n3) to docosahexanoic acid (C22-6 n3).
By international convention, this group of fatty acids with extraordinary physiological importance is known as LCPs (for long-chain 12olyunsaturated fatty acids). These fatty acids with 20 to 22 C atoms are derived from the essential C18 fatty acids and have at least two double bonds in the acyl radical. The abbreviation LCP will be used below for this group of fatty acids, and a distinction is made between w6 LCPs and w3 LCPs.
The LCPs have versatile biological effects. For instance, they are an indispensable component of all the cell membranes in the body. A change in the membrane lipid composition can cause a great variety of physiological problems.
In recent years, the eicosanoids (prostaglandins, leukotrienes, prostacyclins and thromboxanes) synthesized in the organism from some LCPs have gained particular attention. It has been demonstrated that this highly active group of eicosanoids, in low concentrations, is involved in a number of physiological processes.
In infants and children, in comparison to adults, because of the relatively high need for growth and low reserves, the danger exists of a deficiency in these LCPs. In the last trimester of intrauterine fetal development and during postnatal development of the newborn, large amounts of w6 and w3 LCPs are accumulated in the organs. The capacity for synthesis of the LCPs from the essential precursors appears limited in the young infant, however, because of immaturity of the desaturating enzyme system.
2. Description of the Prior Art
Since these LCP fatty acids are virtually entirely absent from infant formulas previously available, formulas have recently been developed that are enriched with these fatty acids; see German Patent Disclosure DE 39 20 679 A1, for instance.
Because of the increased interest in LCPs, there has been an increased demand for sources of raw materials for such long-chain polyunsaturated fatty acids. The oils containing LCPs that are currently available are quite predominantly obtained from marine cold water fish (see European Patent Disclosure EP 0 292 846 A2 and German Patent Disclosure DE 39 40 239 A1). Such oils from the muscle tissue or organs of fish are distinguished by high proportions of w3 LCPs and in particular of eicosapentanoic acid (20-5 n3) and docosahexanoic acid (22-6 n3). Such oils and particularly oils from fish organs have the disadvantage, however, of a high cholesterol content and also a high content of fat-soluble vitamins and possibly fat-soluble pollutants (heavy metals and pesticides).
It has also already been proposed that LCPs be obtained from autotrophically or heterotrophically fermented microorganisms (see International Patent Disclosures WO 91/07498 and WO 91/119 182 and German Patent Disclosure DE 34 46 795 A1).
The LCPs of interest here can moreover be obtained from organ fats of livestock (cattle/pigs) and from the yolk of chicken eggs (EP 0 074 251 B2). The extraction of LCPs from human placentas is described in EP 0 140 805 A1.